Method and apparatus for briquetting coal



Feb. 20, 1962 H. HULLEN 3,022,146 METHOD AND APPARATUS FOR BRIQUETTING COAL Filed Sept. 9, 1957 5 i :5 H 40 A j U lA/VE/VTOR B9: WM

RYTOR N E 3 ilnited States Patent 3,022,146 METHOD AND APPARATUS FOR BRIQUEITING CGAL Hermann Hullen, Grevenbroich, Germany, assignor to Maschinenfabrik Buckau R. Wolf Aktiengesellschaft, Grevenbroich, Germany Filed Sept. 9, 1957, Ser. No. 682,930 Claims priority, application Germany Sept. 13, 1956 8 Claims. (Cl. 4413) The present invention relates to a method and apparatus for briquetting coal, and more particularly, it relates to a method and apparatus for briquetting hard coal and also hard lignite of relatively high bitumen content without using a binder material.

Up to now the successful briquetting of coal without addition of a binder material was only possible in the case of coal of low gas content including only up to 12% of gas-containing or gas-forming constituents. Thus, briquetting of coal Without the addition of a binder material was primarily only possible with coal of anthracite type.

According to one of these known methods, 80 parts of lean coal having a particle size of up to 3 mm. are heated to 435 C. and are then mixed with 20 parts of coal dust having a particle size of up to 0.2 mm. and having been heated to a temperature of about 250 C. The thus formed mixture is then immediately briquetted. According to the above method only lean coal can be briquetted and even then the results are rather unsatisfactory since the relatively large particles of lean coal having the size up to 3 mm. require an undue length of time for being carefully heated to 435 C., or, if the same are to be quickly heated, have to be exposed to very high temperatures. In both cases, i.e. upon prolonged heating or upon exposure to very high temperatures, deterioration and decomposition of the coal substance takes place which reduces the briquettability of the lean coal, primarily due to unavoidable losses of gas, i.e. bituminous substance. In this connection, it has to be considered that the original gas or bitumen content of lean coal is already so small as to make briquetting without the addition of binder material a diificult undertaking.

According to another method, the entire mass of coal particles is to be quickly heated to a high temperature prior to briquetting. The heating is to be carried out within the period of one minute.

When it is attempted to form briquettes of fat hard coal rich in gas-forming constituents, i.e. hard coal containing more than 12 to 15% of gas forming bituminousconstituents, it is caused that upon heating to the required briquetting temperature which generally lies between 300 and 450 C., the gas-forming constituents of the coal volatilize and the thus freed gaseous hydrocarbons create upon briquetting a gas pressure sufficiently high to form cracks in or even to burst the briquettes. Such damaged briquettes are largely usefuless for industrial purposes.

It is, therefore, an object of the present invention to overcome the above mentioned ditiiculties particularly in the briquetting of fat, bitumen-rich coal.

It is another object of the present invention to provide a method by which coal rich in gas-forming constituents can be eliectively briquetted in a simple and economical manner and without the addition of binder material.

It is a further object of the present invention to provide an apparatus for the binder-free briquetting of gas-rich coal.

Other objects and advantages of the present invention will become apparent from a further reading of the description and the appended claims.

With the above and other objects in view, the present invention comprises a process of forming briquettes of bitumen-containing coal, comprising the steps of heating a mass composed of smaller and larger particles of the coal to a first elevated temperature being below the softening point of the coal, separating the smaller particles of the mass from the larger particles thereof, further heating the separated smaller particles to a second elevated temperature being above the softening point of the coal so as to soften the smaller particles, intimately mixing the further heated softened smaller particles with the notfurther heated unsoftened larger particles, and briquetting the thus-formed intimate mixture of softened and unsoftened particles, whereby the softened smaller particles serve as binder for the unsoftened larger particles and substantially split-free briquettes are formed in the absence of a binder material.

The present invention also contemplates a briquetting arrangement, comprising, in combination, first heating means for heating a mass composed of smaller and larger particles of coal to a first elevated temperature, separating means for separating the smaller particles of the heated mass from the larger particles thereof, second heating means for further heating the separated smaller particles to a second elevated temperature being higher than first elevated temperature, mixing means for intimately mixing the further heated smaller particles with the not-further heated larger particles, and briquetting means operatively connected to the mixing means for briquetting the intimate mixture of the further heated smaller particles and the not-further heated larger particles.

According to the present invention, briquettes are produced of fat and gas-rich coal which has been reduced in size so that the largest particle of the coal mass preferably do not exceed 3 mm., the mass, of course, also containing particles of progressively smaller sizes. The coal referred to above may either be hard coal or relatively hard, i.e. bitumen-rich lignite.

According to the'present invention, the mass of coal preferably consisting of individual particles of varying sizes, the largest preferably being between about 2 and 3 mm. in size, is heated to a temperature of between about 25 and 50 C. below the softening point of the coal. This heating is preferably carried out within a period of between 3 and 5 minutes by passing through the mass of coal particles a stream of heated inert gas. The term inert gas is meant to denote any gas which substantially will not react with the coal particles. The rate of fiowof the gas is to be so adjusted that between about 20 and 40% of the total mass of coal constituting the smallest particles thereof wili be carried along With the gas stream so that simultaneously with the heating of the entire mass of coal also a separation into larger and smaller particles thereof takes place. The heating time is kept preferably within the range of between 3 and 5 minutes, the exact heating time to be determined in every case depending on the bitumen content of the coal mass. Similarly, the relative quantity of smaller particles which are to be carried away by the hot inert gas stream is adjusted in any given case depending on the bitumen content of the coal, preferably within the range of between 20 and 40% by weight of the entire coal mass. Once the percentage of fines which are to be carried away by the gas stream has been determined, the speed and rate of flow of the gas is so adjusted as to carry away the desired percentage of smaller coal particles. The thus separated smaller coal particles are then quickly further heated to a temperature of between 30 and 50 C. above the softening point of the particular coal. This further heating is preferably carried out Within a time period not exceeding 5 seconds. Thereafter, the superheated smaller coal particles having a temperature above the softening point of the coal are mixed with the large coal particles having a temperature somewhat below the softening point, and the thus-formed mixture is immediately briquetted. V

In this manner, according to the present invention, it is possible to produce faultless briquettes of fat coal, rich in gas-forming bituminous constituents without adding a binder material thereto since the larger coal particles are heated only to a relatively low temperature somewhat below the softening point, at which relatively low temperature no or no appreciable quantifies of briquettedestroying or crack-forming gaseous hydrocarbons are freed, and furthermore losses of volatilizable constituents do not take place or are limited to an insignificant amount. The smaller particles or coal dust which are heated in a relativelyavery short period of time to a temperature above the softening point form gaseous hydrocarbons which, however, condense during the immediately following mixing of the superheated fine coal particles with the larger coal particles having a temperature below the softening point of the coal. The larger coal particles thereby substantially absorb the heat which is freed upon condensation of the volatilized hydrocarbon constituents of the superheated smaller coal particles. In this manner, according to the present invention, it is possible to overcome the previous difficulties in the briquetting of fat coal rich in gas-forming constituents, and the thus-formed briquettes which do not contain any addition of binder material possess the stability required for economic production and industrial use. 7

The method of the present invention also has advantages with respect to the heat economy of the briquette forming process. The entire coal mass is heated to a relatively low temperature below the. softening point of the coal, while, according to the prior method it was necessary to heat the entire coal mass to a temperature above the briquetting temperature, i.e. above the softening point of the coal. Consequently, the quantity of inert heating gas required according to the present invention is considerably reduced. For the further heating or superlast discussed arrangement, the inert heating gases move heating of the smallercoal particles or fines which are separated from the preheated coal mass',-only a small amount of heat has to be supplied since the temperature of the separated smaller coal particles rises further while the same are carried away in the hot gas stream. It should be noted that the briquetting process is improved by reducing the time required for the superheating of the separate smaller coal particles and the subsequent mixing of the smaller and larger coal particles and the briquetting of the thus-formed mixture.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which the FIGURE represents a schematic illustration of a briquetting arrangement according to the present invention.

'Referring now to the drawing, a bunker 1 is shown from which the coal mass consisting preferably of smaller and larger particles, the largest particles having the size preferably not exceeding 3 mm., passes through a proportioning device 2, such as a rotor feeder, to a first heating means which includes a furnace 3 which furnace is adapted for heating granular material. Furnace 3 may, for instance, be a revolving cylindrical furnace or a fiuosolids furnace or the like. Inert heating gas such as, for instance, flue gases pass through furnace 3 as indicated by arrow (3., Conventional devices (not indicated in the drawing) are provided for controlling the temperature and rate of fiow of the inert heating gas to furnace 3. A conduit 4 connects furnace 3 with cyclone 5. The heating gases 3 after passing through furnace 3 and carrying the smaller particles of the coal mass in an amount of preferably between 20 and 40% by weight of the entire mass of the examples.

of coal pass through conduit 4 to cyclone 5 in which separation of at least a portion of the inert heating gases from the fine coal particles takes place. A conduit 7 is provided connecting furnace 3 with mixer 8 for conveying the larger coal particles after the same have been heated in furnace 3 to a temperature below the softening point of the coal, preferablybetween 25 and 50 C. below the softening point of the coal, to mixer 8. The smaller coal particles after being separated in cyclone 5 from the inert heating gas, pass through the second heating means 6 such as an electric furnace or infra-red radiator, to mixer 8. Second heating means 6 is adapted to further heatthe smaller coal particles in a very short period of time preferably within less than 5 seconds to a temperature of about 30-50" C. above the softening point of the coal.

The larger coal particles having a temperature of about 25-50" C. below the softening point of the. coal and the smaller coal particles having a temperature. of about 3040 C. above the softening point of the coal thus both enter mixer 8 in which an intimate mixture of the larger and smaller coal particles is'formed. The thusformed mixture then passes immediately into briquette press 9.

In case flue gases'for heating the coal in furnace 3 are not available or other thanv flue gases are to be used for the heating of the coal mass for some other reason, it is preferred, according to the present invention, to include in the briquetting arrangement a gas heater it) arranged in a conduit 11 leading from cyclone 5 to furnace 3. In any event, the heating gases are separated from the smaller coal particles in cyclone 5 and leave cyclone 5 as indicated by arrow K. According to the in a closed cycle from furnace 5 through conduit 4 to cyclone 5 and from there through conduit 11 to gas heater It) back to furnace 3 so that the inert gas is used in economical manner as a circulating heat carrier. Nitrogen for instance may be used as inert gas.

The following examples of the process of the present invention are given as illustrative'only, the present invention, however, not being limited to the specific details Example The prepared coal which has been reduced to a maximum particle size of 3 turn; is filled into bunker 1 and is allowed to pass from there through rotor feeder 2 in measured quantities into revolving cylindrical furnace 3. Flue gases enter'furnace 3 from the opposite end thereof in such quantity and at such temperature that the mass of coal particles is heated within a period of between 3 and 5 minutes to a temperature of between 25 and 50 C. below the softening point of the coal, i.e. below the temperature at which the coal is sufficiently plasticized for briquet-ting thereof. The length of time required for the heating of the coal as Well as the briquetting temperature depend on the content of the coal of bituminous constituents and have to be determined experimentally from case to .case. Highly bituminous coal is, for instance, heated during a period of 5 minutes to a temperature of 250 C., while coal of lesser fat content is heated in only 3minutes to 350 C. According to the illustrated embodiment, fine gases and coal are countercurrently introduced into the furnace 3. It is, however, of course also possible and within the scope of the present invention to conduct the heating gases and the coal in parallel flow.

After the mass of coal particles has been heated in furnace 3 to the required temperature (below the softening point of the coal), a portion of between 20 and 40% of the thus preheated coal consisting of the smaller particles thereof, is carried by the flue gases as coal fines or dust through conduit 4 into cyclone 5. in cyclone 5, the flue gases are separated from the coal fines. The gases leave cyclone 5 as indicated by arrow K while the coal fines pass through heater 6 in which the same'are heated within a period of time not exceeding 5 seconds to a temperature of between 30 and 50 C. above the softening point of the coal, i.e. above the briquetting temperature thereof. In the case of highly bituminous coal only about 20% are separted as fines or dust and pass through infra-red radiator 6. In this connection, it has to be noted that the softening point or briquetting temperature of coal of lesser fat content is somewhat higher than the softening point of highly bituminous coal.

While the smaller coal particles are thus further heated, the preheated larger coal particles pass through conduit 7 into mixer 8 which is arranged adjacent to infra-red radiator 6 and preferably directly above briquette press 9. In mixer 8, the larger and smaller coal particles which were separated from each other in furnace 3 are reunited and intimately mixed together. Immediately thereafter, the thus-formed mixture is pressed into briquettes.

Example 2 Highly bituminous coal having a softening point of about 300 C. and containing about 40% volatilizing constituents is reduced to maximum particle size of 3 mm. and within 5 minutes heated to 250 C. The speed of flow of the inert heating gas passing through the coal, as well as the quantity of heating gases and the temperature thereof are so adjusted that the heating gases separate and carry away from the mass of coal particles 20% thereof in the form of dust or coal fines. The thus separated smaller coal particles are then separated from the heating gases and further heated in not more than 5 seconds to a temperature of 350 C. i.e. to a temperature which is about 50 C. higher than the softening point of the coal. Within 3 seconds after thus further heating of the separated smaller coal particles, the same are intimately mixed with the preheated larger coal particles and the thus-formed mixture is immediately pressed into briquettes.

Example 3 Coal of relatively low fat content, having a softening point of about 400 C. and containing about 16% volatilizable constituents is reduced to a maximum particle size of 2 mm. and heated within a period of 3 minutes to a temperature of 350 C. The speed of flow of the inert gases used for heating the mass of coal particles, as well as the temperature and quantity thereof are so adjusted that the inert heating gases separate and carry away from the mass of coal particles 40% of the smaller particles thereof. The thus separated smaller coal particles are separated from the inert heating gases carrying the same and are further heated in less than 5 seconds to a temperture of 430 C., i.e. to a temperature approximately 30 C. above the softening temperature of the coal. The thus further heated smaller coal particle-s are reunited and intimately mixed with the preheated larger coal particles within a period of time not exceeding 3 seconds and the thus-formed intimate mixture is immediately pressed into briquettes.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

l. A process of forming briquettes of a particulate mass consisting of fat coal containing more than 12% gas forming bituminous constituents, comprising the steps of heating a mass composed of smaller and larger particles of said coal the largest particles of said coal having a size not exceeding about three millimeters to a first elevated temperature being below the softening point of said coal; separating said smaller particles of said mass so as to separate between about 20% and 40% by weight thereof from said larger particles thereof; further heating said separated smaller particles to a second elevated temperature being above the softening point of said coal so as to soften said smaller particles while maintaining said larger particles of said mass in unsoftened state; intimately mixing said further heated softened smaller particles with said not-further heated unsoftened larger particles; and briquetting the thusformed intimate mixture of softened and unsoftened particles, whereby said softened smaller particles serve as binder for said unsoftened larger particles and subtantially split-free briquettes are formed in the absence of a binder material.

2. A process of forming briquettes of a particulate mass consisting of bitumen-containing coal containing more than 12% gas forming bituminous constituents, comprising the steps of heating a mass composed of smaller and larger particles of said coal the largest particles of said coal having a size not exceeding about three millimeters to a first elevated temperature being between 25 and 50 C. below the softening point of said coal; separating said smaller particles in a quantity of between 20 and 40% of said mass from said larger particles thereof; further heating said separated smaller particles to a second elevated temperature being between 30 and 50 C. above the softening point of said coal so as to soften said smaller particles while maintaining said larger particles of said mass in unsoftened state; intimately mixing said further heated softened smaller particles with said not-further heated unsoftened larger particles; and briquetting the thus-formed intimate mixture of softened and unsoftened particles, whereby said softened smaller particles serve as binder for said unsoftened larger particles and substantially split-free briquettes are formed in the absence of a binder material.

3. A process of forming briquettes of a particulate mass consisting of bitumen-containing coal containing more than 12% gas forming bituminous constituents, comprising the steps of heating a mass composed of smaller,

and larger particles of said coal the largest particles of said coal having a size not exceeding about three millimeters within a period of between three and five minutes to a first elevated temperature being between 25 and 50 C. below the softening point of said coal; separating said smaller particles in a quantity of between 20 and 40% of said mass from said larger particles thereof; further heating said separated smaller particles within a period not exceeding five seconds to a second elevated temperature being between 30 and 50 C. above the softening point of said coal so as to soften said smaller particles while maintaining said larger particies of said mass in unsoftened state; intimately mixing said further heated softened smaller particles with said not-further heated unsoftened larger particles; and briquetting the thus-formed intimate mixture of softened and unsoftened particles, whereby said softened smaller particles serve as binder for said unsoftened larger particles and substantially split-free briquettes are formed in the absence of a binder material.

4. A process of forming briquettes of a particulate mass consisting of bitumen-containing coal containing more than 12% gas forming bituminous constituents, comprising the steps of heating a mass composed of smaller and larger particles of said coal the largest particles of said coal having a size not exceeding three millimeters within a period of betwen about three and five minutes to a first elevated temperature being between 25 and 50 C. below the softening point of said coal; separating said smaller particles of said mass in a quantity of between 20% and 40% from said larger particles thereof; further heating said separated smaller particles within a period not exceeding five seconds to a second elevated first heating means for particles while maintaining said larger particles of said mass in unsoftened state; intimately mixing said further heated softened smaller particles with said not-further heated unsoftened larger particles; and briquettingthe thus-formed intimate mixture of softened and unsoftened particles, whereby said softened smaller particles serve as binder for said unsoftened larger particles and substantially split-free briquettes are formed in the absence of a binder material. a

5. A briquettingapparatus, comprising, in combination, heating a mass composed of smaller and larger particles of coal to a first elevated temperature; feeding means for introducing measured portions of said mass of coal into said first heating 'means; separating means for separating said smaller particles of said heated mass from said larger particles thereof; second heating means for further heating said separated smaller particles to a second elevated temperature being higher than said first elevated temperature; mixing means for intimately mixing said further heated smaller particles with said not-further heated larger particles; conduit means operatively' connected to said first and second heating means and said mixing means for conveying said separated larger and smaller particles to said mixing means and briquetting means operatively connected to said mixing means for. briquetting said intimate mixture of said further heated smaller particles and said not-further heated largerparticles.

6. A briquetting apparatus, comprising, in combination, a furnace adapted for heatinggranular material to a first elevated temperature; 'means for introducing a mass composed of smaller and larger particles of coal into said furnace; means for passing a stream of hot gas through saidfurnace so as to heat said mass of coal particles in contact with said hot gas to said first elevated temperature and to carry said smaller particles of coal along with said stream of hot gas thus separating said heated smaller particles from said heated larger particles or" said mass of coal; means for separating hot gas from said smaller coal particles; means for further heating said separated smaller particles to a second elevated temperature being higher than said first elevated temperature;

mixing means for intimately mixing said further heated smaller particles with said not-further heated larger particles; and briquetting means operatively connected to 1 said mixing means for briquetting said intimate mixture of said further heated smaller particles and said not-fur? ther heated larger particles.

7. A briquetting apparatus, comprising, in combination, a furnace adapted for heating granular material to a first elevated temperature; means for introducing a mass composed of smaller and larger particles of coal into said said stream of hot gas thus separating said heated smaller particles from said heated larger particles of said mass ofcoal; means for separating at least a portion of said gas from said smaller particles'of coal; means for further heating said separated portion of said gas; means for reintroducing said further heated separated portion of said gas into said furnace; means for further heating said separated smaller particles to a second elevated temperature being higher than said first elevated temperature; mixing means for intimately mixing said further heated smaller particles with said not-further heated larger particles; and briquetting means operativelyconnected to said mixing means for briquetting said intimate mixture of said further heated smaller particles and said not-further heated larger'particles.

8. A briquetting apparatus, comprising, in combination, a furnace adapted for heating granular material to a first elevated temperature; means for introducing a mass composed of smaller and larger particles of coal into said furnace; means for passing a stream of hot gas through said furnace so as to heat said mass of coal particles in contact with said hot gas to said first elevated temperature and to carry said smaller particles of coal along with said stream of hot gas thus separating said heated smaller particles from said heated larger particles of said mass of coal; means for separating at least a portion of said gas from said smaller particles of coal; means for further heating said separated portion of said gas; means for reintroducing said further heated separated portion of said gas into said furnace; means for further heating said separated smaller particles to a second elevated temperature being higher than said first elevated temperature; mixing means for intimately mixing said further heated smaller particles with said not-further heated larger particles; conduit means operatively connected to said furnace and said heating means and said mixing means for conveying said separated larger and smaller particles to said mixing means; and briquetting means operatively connected to 914,523 Shepard Mar. 9, 1909 1,481,627 Smith Jan. 22, 1924 2,937,080 Komarek'et, al; V May 17, 1960 FOREIGN' PATENTS Australia of 1930 

5. A BRIQUETTING APPARATUS, COMPRISING, IN COMBINATION, FIRST HEATING MEANS FOR HEATING A MASS COMPOSED OF SMALLER AND LARGER PARTICLES OF COAL TO A FIRST ELEVATED TEMPERATURE; FEEDING MEANS FOR INTRODUCING MEASURED PORTIONS OF SAID MASS OF COAL INTO SAID FIRST HEATING MEANS; SEPARATING MEANS FOR SEPARATING SAID SMALLER PARTICLES OF SAID HEATED MASS FROM SAID LARGER PARTICLES THEREOF; SECOND HEATIG MEANS FOR FURTHER HEATING SAID SEPARATED SMALLER PARTICLES TO A SECOND ELEVATED TEMPERATURE BEING HIGHER THAN SAID FIRST ELEVATED TEMPERATURE; MIXING MEANS FOR INTIMATELY MIXING SAID FURTHER HEATED SMALLER PARTICLES WITH SAID NOT-FURTHER HEATED LARGER PARTICLES; CONDUIT MEANS OPERATIVELY CONNECTED TO SAID FIRST AND SECOND HEATING MEANS AND SAID MIXING MEANS FOR CONVEYING SAID SEPARATED LARGER AND SMALLER PARTICLES TO SAID MIXING MEANS AND BRIQUETTING MEANS OPERATIVELY CONNECTED TO SAID MIXING FOR BRIQUETTING SAID INTIMATE MIXTURE OF SAID FURTHER HEATED SMALLER PARTICLES AND SAID NOT-FURTHER HEATED LARGER PARTICLES. 